The objective of this study is to determine the functions of a recently discovered and characterized group of cellular retinoid-binding proteins. More specifically, we will examine the interactions of cellular binding proteins specific for retinol, retinal and retinoic acid with enzymes, proteins and compartments known to be important in the metabolism of vitamin A in ocular tissues. Such interactions might lead to transfer of the bound retinoid from a binding protein to an enzyme or protein, utilization of a bound form of the vitamin as a substrate in an enzymatic transformation (dehydrogenation, isomerization, esterification, etc.), transport of retinol between intracellular compartments or neural retina and retinal pigment epithelium or perhaps the transfer of retinol from the serum retinol-binding protein to a cellular retinoid-binding protein. The uptake and metabolism of retinol in cultured retinoblastoma cell lines Weri-Rb1 and Y-79 will be examined as these cell lines may serve as model systems for the metabolism of vitamin A in retina. Particular emphasis will be placed on characterizing the enzyme responsible for esterification of retinol and the source of acyl groups for their reactions.